This invention relates to a process for the production of quaternary ammonium salts of fatty acid hydroxyalkanesulfonic acids, in which a hydroxyalkanesulfonic acid is subjected to the condensation reaction with a C.sub.6-18 fatty acid at elevated temperature and reduced pressure, any water of solution present and the water of reaction formed are directly removed from the reaction mixture and the fatty acid hydroxyalkanesulfonic acid is reacted with a base to form the corresponding quaternary ammonium salt of the fatty acid hydroxyalkanesulfonic acid. 2. Description of the Related Art
Fatty acid hydroxyalkanesulfonic acid salts, more particularly fatty acid isethionates in the C.sub.12-14 chain length range, are anionic surfactants with only minimal sensitivity to hardness, high foaming and wetting power and excellent compatibility with the skin. More particularly, they are distinguished by the fact that the skin can be cleansed without overly drying out. In addition, the soaps containing these compounds can even be used by people unable to tolerate typical high pH soaps. Accordingly, these compounds are used in cosmetic preparations and cleansing formulations
Commercial fatty acid hydroxyalkanesulfonic acid salts are generally produced from the corresponding salt of hydroxyalkanesulfonic acid by reaction with the fatty acid in the presence of an esterification catalyst, for example ZnO, at temperatures of up to 250.degree. C. However, dark-colored products are obtained in the production of ammonium fatty acid hydroxysulfonic acid salts by this process.
The fatty acid isethionates, particularly the sodium fatty acid isethionates frequently used, show only limited solubility in water which restricts their use to soaps, such as syndets and combination bars and opaque liquid formulations.
Quaternary ammonium salts of fatty acid hydroxyalkanesulfonic acids, more particularly ammonium fatty acid isethionate, are highly soluble in water and may be used in clear liquid formulations. However, this possibility is impaired by the fact that the quaternary ammonium salts of fatty acid isethionic acid prepared by conventional methods are dark in color so that, in the absence of bleaching, the liquid formulations containing them are also dark in color.
The problem addressed by the present invention was to provide a process for the production of quaternary ammonium salts of fatty acid hydroxyalkanesulfonic acids which would enable these compounds to be obtained in high yields and in light-colored highly concentrated form.